1. Field of the Invention
The present invention relates to a radiation sensitive resin composition comprising a specific siloxane resin and a specific fluorine-containing resin suitable for microprocessing using various types of radiation such as deep ultraviolet radiation, electron beams, and X-rays.
2. Description of Background Art
A recent strong demand for high density and highly integrated LSIs accelerates miniaturization of wiring patterns.
Using short wave rays in a lithographic process is one method for miniaturizing wiring patterns. In recent years, deep ultraviolet rays typified by a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), or an F2 excimer laser (wavelength: 157 nm), electron beams, X rays, and the like are being used in place of ultraviolet rays such as g-line (wavelength: 436 nm) and i-line (wavelength: 365 nm).
Novolac resins, poly(vinylphenol) resins, and the like have been conventionally used in resist compositions. However, because these resins exhibit strong absorbance at a wavelength of 193 nm due to inclusion of aromatic rings in the structure, a lithographic process by an ArF excimer laser, for example, using these resins cannot provide high accuracy corresponding to high photosensitivity, high resolution, and a high aspect ratio.
Therefore, a resin material for use in a resist, transparent to a wavelength of 193 nm or less, particularly to an ArF excimer laser (wavelength: 193 nm) or an F2 excimer laser (wavelength: 157 nm), and exhibiting excellent dry etching resistance equivalent to or better than aromatic rings has been desired. A polysiloxane is one such polymer. R. R. Kunz et al. of the MIT have reported their research results showing excellent transparency of a siloxane polymer at a wavelength of 193 nm or less, particularly at 157 nm, commenting on superiority of this polymer as a resist material in a lithographic process using radiation with a wavelength of 193 nm or less (e.g. J. Photopolym. Sci. Technol., Vol. 12, No. 4, 1999, P. 561-570, SPIE, Vol. 3678 (1999), P. 13-23). Moreover, polysiloxane polymers are known to exhibit excellent dry etching properties. In particular, a resist containing polyorganosilsesquioxane having a ladder structure is known to possess high plasma resistance.
Several chemically amplified resist compositions using a siloxane polymer have also been reported. A radiation-sensitive resin composition comprising a polysiloxane having an acid-dissociable group such as a carboxylic acid ester group, phenol ether group, etc., on the side chain, bonded to a silicon atom via one or more carbon atoms has been disclosed (e.g. Japanese Patent Application Laid-open No. 323611/1993). However, this polysiloxane cannot provide high resolution if the acid-dissociable carboxylic acid groups on the side chain do not efficiently dissociate. If a large number of acid-dissociable groups dissociate, on the other hand, the curing shrinkage stress of the resist film increases, causing cracks and peels in the resist film.
A positive tone resist using a polymer in which the carboxyl group of poly(2-carboxyethylsiloxane) is protected with an acid-dissociable group such as a t-butyl group has also been disclosed (Japanese Patent Application Laid-open No. 160623/1996). Since this resist protects the carboxyl groups only insufficiently, it is difficult to develop the resist containing a large amount of carboxylic acid components remaining in the non-exposed area using a common alkaline developing solution.
A resist resin composition containing a polyorganosilsesquioxane having an acid-dissociable ester group has also been disclosed (e.g. Japanese Patent Application Laid-open No. 60733/1999). This polyorganosilsesquioxane is prepared by the addition reaction of an acid-dissociable group-containing (meth)acryl monomer to a condensation product of vinyl trialkoxysilane, γ-methacryloxypropyltrialkoxysilane, or the like. The resin has a problem of insufficient transparency to light with a wavelength of 193 nm or less due to unsaturated groups originating from a (meth)acrylic monomer remaining on the polymer side chains. The patent specification also describes a resist resin composition containing a polymer made by the esterification of polyhydroxycarbonylethylsilsesquioxane with t-butyl alcohol. This polymer also has the same problem as a resist as encountered by the polymer disclosed in Japanese Patent Application Laid-open No. 160623/1996 due to a low degree of carboxyl group protection.
More recently, Japanese Patent Applications Laid-open No. 2000-221685 and No. 2000-221686 have disclosed chemically amplified resists in which the resin component contains a siloxane-based resin or silicon-containing resin and a silicon-free resin, such as a resist containing a silsesquioxane polymer and a copolymer of 2-methyl-2-adamantyl methacrylate and mevalonic methacrylate or a resist containing a copolymer of p-hydroxystyrene and tris(trimethylsilyl)silyl methacrylate and a copolymer of p-hydroxystyrene and t-butyl methacrylate. The inventors of these patent applications claim that these chemically amplified resists excel in sensitivity, resolution, pattern-forming properties, dry etching resistance, and the like.
Most recently, due to progress of miniaturization of resist patterns LER (line-edge roughness) is being highlighted as an important property of chemically amplified resists, including the chemically amplified resist containing a siloxane polymer. A technology for decreasing the LER is strongly desired.
An object of the present invention is to provide a radiation-sensitive resin composition suitable for use particularly as a chemically-amplified resist exhibiting high transparency at a wavelength of 193 nm or less and excellent LER properties.